System and method for the transfer of cryogenic fluids

ABSTRACT

A system and method for the transfer of cryogenic fluid fuel includes a nozzle positionable with respect to fuel tank inlet, e.g., of an unmanned aerial vehicle (UAV), a seal to seal the area where the nozzle and inlet are connected, a collapsible and expandable bellows providing an isolation volume where the fluid is transferred from the nozzle into the inlet; a vacuum is provided in the volume to avoid accumulation of fuel or other species in the volume.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.16,987/602, filed on Aug. 7, 2020, which is a divisional of U.S. Pat.No. 15,606,201, filed on May 26, 2017, which claims priority to U.S.Provisional Patent Application No. 62/343,003, filed on May 29, 2016,the entire disclosures of which are hereby incorporated by reference.

TECHNICAL FIELD

The present application is directed to the transfer of cryogenic fluidsand, more particularly, to a system and method for autonomous liquidhydrogen vehicle refueling.

BACKGROUND

There are many types of Unmanned Aerial Vehicles (UAVs), which are alsoknown as drones. Types of UAV vehicles include multirotors, small handthrown fixed-wing planes, medium sized vehicles that can be catapultlaunched or take off from short runways or very large vehicles that canfly around the world conducting reconnaissance missions and launchingmissiles. A new breed of vehicle called UCAVs for Unmanned Combat AirVehicles can take off and land on aircraft carriers.

One of the main challenges for UAVs is flight duration. Typical UAVs usebatteries or internal combustion engines for propulsion. Batteries areextremely heavy for driving propellers with electric motors, andinternal combustion engines are very inefficient at converting aviationfuels (hydrocarbon based) to drive propellers mechanically thus limitingflight duration. A more efficient propulsion system is one that useshydrogen fuel that is light weight and has the highest stored energycontent per unit mass compared to other fuels. By using a very energyefficient fuel cell to convert the hydrogen into electricity to drivethe electric motors, extreme durations can be achieved. Table 1 is acomparison of flight duration for the various power systems as modeledfor the same aircraft. The power system with the greatest duration is afuel cell with liquid hydrogen storage.

TABLE 1 Power/Energy Source for 12 Flight ft. Wing Span UAV DurationBatteries  <1 hour Internal Combustion Engine    3 hours with AviationFuel Fuel Cell with Gaseous Hydrogen Storage   13 hours Fuel Cell withLiquid Hydrogen Storage >30 hours

Liquid hydrogen has a density of 70 kg/m′ when stored at 21 Kelvin at 1atmosphere of pressure. This is a density increase of 2.8 times comparedto compressed hydrogen gas storage at 350 bar (5,100 psi) at ambienttemperature. Liquid hydrogen is vaporized and warmed using ambienttemperatures and a heat exchanger and then is consumed by the fuel cellto make electricity and water, which is released over-board. The fuelcell is typically a Proton Exchange Membrane (PEM) fuel cell, whichoperates at around 60° C.

A liquid hydrogen powered UAV needs to have fuel transferred into theUAV liquid hydrogen tank from a storage dewar. The transfer processstarts by pressurizing the storage dewar with warm gaseous hydrogen alsocalled autogenous pressurization. The warm gaseous hydrogen comes fromwithdrawing some of the stored liquid and warming it up in a vaporizer.The gas space above the liquid (ullage space) is then pressurized.Pressurization of the storage or supply dewar can be conducted using agas other than hydrogen such as helium that does not condense in theliquid, which is called non-condensable pressurization. A liquid supplyvalve is then opened and the pressure pushes the liquid out of thestorage dewar and into the UAV liquid hydrogen tank, which is vented toatmospheric pressure during the filling process. Alternatively, a pumpcan be used to transfer the liquid hydrogen. A comparison of these twoprior art processes for transferring liquid hydrogen are shown in FIG.1.

The transfer equipment used includes transfer lines that are vacuumjacketed and are connected to the dewars with bayonet fittings. Thetransfer of liquid hydrogen is currently a manual process that involvesmany hands-on steps. These steps include: physically connecting uptransfer equipment such as hoses, flanges, fittings, and bayonets; andconducting flow or pressure purges of the system prior to and after thetransfer process in order to maintain cleanliness and to mitigate thegeneration of combustible mixtures of air and hydrogen. The purgesinvolve connecting up the purge gas source, opening and closing valves,and monitoring pressures per specific predetermined values based on thevolume of the system being purged. In the case of flow purges the timeof the flow process is measured based on the volume of the system andthe flow rate of the purge gas. The flow rate of the purge gas ismeasured either by the pressures across the flow valve or a flowmeasuring device. Vacuum purges may also be done, which require the useof a vacuum pump. The vacuum pump hose is connected to the pump-out portand the vacuum level is measured via a thermocouple bulb or a variety ofdifferent vacuum gauges suitable for the vacuum range specified for thepurge. The vacuum pump then may need to be disconnected from the system.

When the liquid hydrogen transfer lines get cold, moisture or residualgases will condense and potentially freeze on the cold surfaces. Heliumgas is typically used as a purge gas because it has a lower condensationpoint than liquid hydrogen and is thus called a noncondensable gas inthe presence of liquid hydrogen.

INTRODUCTION SUMMARY

Drones that require long duration operation using traditional aviationfuels will require in-flight refueling as discussed in U.S. Pat. No.8,056,860. In-flight refueling is a routine operation for skilled andtrained aviators in manned aircraft; however, the '860 patent teachesthat drones typically fly slower, so attempting in-flight refueling frommanned aircraft that fly much faster is not practical. The patentdiscusses drone-to-drone refueling and teaches a method of using amagnetic detection scheme for assisting the guidance and control of thestandard hose and basket refueling mechanism while two aircraft aremoving relative to each other and relative to the ground. Theabove-mentioned U.S. Pat. No. 8,056,860 patent does not teach how totransfer cryogenic fluids or how to use a magnet to mechanically couplethe refueling apparatus with the aircraft fuel tank.

Prior art solutions for in-flight refueling with hose couplings arerepresented by US 2010/0019090 and involved drogues. Drogues aretypically used like parachutes to create drag forces to stabilize therefueling hose trailing from a tanker aircraft in a generally horizontalattitude. They provide drag for a refueling coupling at the trailing endof the refueling hose, which is mated with a fuel probe extending fromthe receiving aircraft. This prior art does not discuss the transfer ofcryogenic fluids.

The general problem of refueling cryogenic tanks resides in the need tomaintain the fluid in a liquid state through the minimization of addingheat to the fluid also known as heat leak. Heat leak can come from manysources including external convection, conduction, and radiation throughpiping, penetrations, insulation, and support structures as well as fromany energy that comes into the cryogenic system from higher temperaturefluids (pressurization fluids) or powered systems (e.g. pumps,instruments).

Heat leak as discussed above that transfers into the dewar will causethe ullage to stratify such that it is at a warmer temperature than thebulk liquid, which can cause measurement issues with knowing thethermodynamic state of the fluid when using tank pressure as the onlymeasurement. U.S. Pat. No. 3,946,572 teaches how to de-stratify theullage through the use of a pump and an internal spray bar such that theullage gas temperature is the same as that of the liquid (also known asa saturated state), which allows the user to only have to measure tankpressure to determine the fluid temperature. Another issue that U.S.Pat. No. 3,946,572 addresses is the ability to maintain a specifichigher pressure and temperature inside the receiver dewar that is higherthan the saturation temperature in the supply dewar. The solution is touse a pump to increase pressure, a heat exchanger to specifically addheat as the fluid transfers to the receiver dewar, and a check valvethat is set to only relieve when a certain pressure is reached. Withthis system configuration both the supply dewar and receiver dewar arecapable of maintaining their desired set points.

Another problem that is encountered during the transfer of liquidcryogens from the supply dewar to the receiver dewar is thecontamination of the cryogenic liquid by residual gases that arecollected as a result of the cryogen production processes. U.S. Pat. No.5,548,962 teaches the cooling of the liquid prior to or during thetransfer to precipitate the solidified residual gases and run themthrough a filter during the liquid transfer process.

One of the major reasons to transfer hydrogen is to refuel vehicles.Prior art is typically focused on the transfer of gaseous hydrogen suchas found in WO 2007/059781 where a system for transferring this hydrogeninvolves the use of a set of tanks and nozzles on a moving track thatconnect to a moving vehicle (an automobile) at which time a telescopingarm connects a nozzle for the transfer of hydrogen. There are severalproblems with telescoping arms and connecting nozzles for the transferof hydrogen that are not addressed in WO 2007/059781, especially for thetransfer of liquid hydrogen. These problems include binding/galling ofmoving parts, thermal contraction mismatch, and leakage caused by theextreme environment of cryogenic (21 Kelvin) temperatures combined withthe transfer pressure. For example, a telescoping nozzle for liquidhydrogen transfer would need to be vacuum jacketed so both the internalpipe and external jacket would need to telescope, which would require aseries of cryogenic moving sealing surfaces and seals to keep thecryogenic liquid hydrogen out of the vacuum space and air from theoutside out of the vacuum space. Moving cryogenic seals are prone toleakage that destroys the vacuum level, which increases heat leak, whichleads to an inefficient transfer of the fluid as it heats up. Inaddition, leaking seals is a safety issue with hydrogen that may lead tocombustion with air if both seals would generate a combustible mixtureinside the telescoping refueling arm. The invention disclosed withinsolves these problems by using a simpler and more reliable approach ofmoving a nozzle to a receptacle through the use of a robotic arm and aflexible cryogenic bellows and hose designed specifically to remain safeand efficient while flexing under cryogenic operations.

Prior art has attempted to describe the process of transferring liquidhydrogen to flying drones from a series of floating balloons high in theatmosphere as presented in U.S. Pat. No. 8,939,396. This patent teachesthe use of balloons that carry equipment to generate hydrogen from waterthat is pumped up to the platforms carried by the balloons and somehowliquefies it. The liquid is then transferred to flying drones. Theproblems this prior art does not address are how the hydrogen gas ismade from solar power, how the hydrogen is liquefied, how the liquidhydrogen is stored, how the transfer system works, and how to connectthe transfer system to the drone.

The transfer of liquid hydrogen from one dewar to another dewar or tankrequires the coupling of each end of the fluid transfer piping or hosesto their respective dewars. The coupling is required for a number ofreasons including the following: transfer liquid between two locations,maintain a leak free flow path, keep contamination out of the fluidsystems, and maintain system pressure. Ideally the coupling will alsominimize that transfer of heat from the environment also known as heatleak. Heat leak eventually migrates through the transfer lines and fromother locations into the dewars where it tends to warm the liquid orullage gas or both. Warming of the fluids is undesirable as it may leadto pressure build up and the need for the tank to relieve pressurethrough a series of relief devices such as relief valves, vent valves,or burst disks. Warming of the liquid also decreases density, whichlimits the quantity of fuel that can be put into the vehicle tank anddecreases vehicle flight duration.

There are a variety of coupling methods that include fittings, flanges,field fit joints, and bayonets. Fittings are not vacuum jacketedinsulated so that wrenches can be applied to mechanically tighten thethreaded connections with a seal or gasket between the compressed parts.Because they are not vacuum jacketed, fittings are a source of high heatleak leading to an inefficient transfer of liquid due to excess boiling,which is undesirable in transferring liquid cryogens, especially liquidhydrogen because each unit mass that is converted from liquid to gasbecomes unusable in the aircraft liquid hydrogen tank and is wasted.

Flanges are considered temporary sealing methods that involve multiplebolts for clamping force so that the interfaces can be disconnected.Flange seals may involve o-rings in grooves or serrated surfaces withflat gaskets. The flanges can be insulated but are not vacuum jacketedand thus have a higher heat leak, which is a similar problem asdescribed for fittings.

Field joints are made by welding two ends of the pipe together making apermanent seal that can then be insulated around and inserted into avacuum jacketed pipe to minimize heat leak. So although the heat leakhas been minimized it becomes very impracticable to disconnect the twopipes that are joined together and these types of joints cannot be usedfor refueling of liquid hydrogen vehicles rapidly.

Finally, cryogenic bayonets are designed to minimize heat leak from atransfer system to the dewar via their long length and the trapping ofgas between the inner and outer thin-walled tubes. Seals are typicallyo-rings at the warm end. The cold end may have a Teflon type seal aswell. Bayonets have a flange on the outer tube that mounts to anotherflange on the tank or dewar. The flanges are connected via bolts or bandclamps. The band clamps are quicker to remove than the bolted flanges.The problem with bayonets is that they are heavy due to the longlengths, vacuum jacketed tubes, flanges, and bolts/clamps, whichsignificantly impact the weight of the aircraft. The invention disclosedwithin solves this problem through the use of a refueling couplingassembly.

Vacuum jacketed valves are used for isolating the flow of cryogenicfluids through piping systems and from tanks. The valves have anadditional housing called the vacuum jacket around the valve to minimizeheat leak into the piping/tank system to keep the liquid from boilingaway. The valve and its associated vacuum jacket are made of metal tosurvive the cryogenic temperatures and handle the pressure and thus arevery heavy. The weight of these valves make it prohibitive to use onUAVs where weight is a critical performance parameter, the more weightthe less performance.

Bellows are used in cryogenic piping systems to allow the passivecontraction and expansion of the pipes as they cool down or warm uprespectively. Bellows are welded in place between two pipes to form apermanent seal that maintains the integrity of the piping system tohandle the pressure, temperature, and flow of cryogenic fluids. Invacuum jacketed piping, bellows are used on the inside pipe as well asthe vacuum jacket (or outer pipe). The bellows in both pipes are weldedin place.

Safe transfer of liquid hydrogen through piping systems requires the useof a noncondensable gas to purge the piping system to remove air andwater vapor prior to the flow of cryogenic liquid hydrogen through thesystem. The non-condensable gas is also used to purge out residualhydrogen gas after the flow of liquid hydrogen is complete in order to“safe” and “clean up” the system. Air removal is a requirement toeliminate the possibility of generating a combustible mixture of oxygenand hydrogen in the system. The only gas that does not condense atliquid hydrogen temperatures is helium. Helium is an expensive gas andis a nonrenewable resource here on Earth. Methods that could be used tominimize or eliminate the use of helium for pre and post liquid hydrogentransfers is highly desirable, which is one problem the disclosedinvention solves. The use of vacuum to remove the air in the system canbe done as well. Nitrogen gas can be used as a purge gas when the pipingsurface temperature is above the saturation temperature of nitrogen atthe piping purge pressure.

SUMMARY

Each of these prior art solutions fails to disclose/teach amethod/apparatus for safe, efficient, and rapid coupling of liquidhydrogen fluid transfer equipment for drones. The system disclosedherein provides specific teachings of how to create a removable vacuumjacketed nozzle through the use of expandable and contractible bellows.It also teaches the specific design of a nozzle and sealing surface thatwhen compressed together by the force of a robotic arm pushing on thebellows form a sealed passage sufficient for the transfer of liquidhydrogen into the drone liquid hydrogen tank and then can be quicklydisconnected, without the need to unbolt or unclamp as discussed inprior art, by simply pulling the nozzle away with the robotic arm toexpand the bellows. The prior art does not teach of a specific couplingmechanism that involves the use of magnets or electro-magnets embeddedin mating flanges that form the vacuum seal around the nozzle and thetank refueling port. The prior art does not teach of a removable capthat is needed during normal flight operations to keep the tankpressurized yet can be used as a pressure relief if the tank overpressurizes. The removable cap eliminates the need on the flight vehiclefor a shut-off valve, which would be heavy, would add mass to the flightvehicle and would require electric power to keep it closed, if it is anormally opened valve thus leading to an energy inefficiency of theoverall vehicle system. The prior art does not teach about a mechanismfor removing the cap, while the vacuum jacket is in place. The prior artdoes not teach a method by which to automatically control each of thesemechanisms and the control of vacuum and nitrogen purge gas at varioussteps in the process. This leads to a safe transfer and eliminates airin the system which could form a combustible mixture with residualhydrogen. The prior art does not teach of the specific measurementsneeded to implement the automated processes such as 1) the displacementof the bellows, 2) the force on the nozzle for sealing, 3) thetemperature of the surfaces within the subsystem for monitoring formoisture freeze out, 4) species sensors for measuring the quantity ofhydrogen in the vacuum space, and 5) the pressure within the vacuumspace for purging and vacuum processes, and a liquid/vapor detector inthe fill nozzle to control the filling process.

Advantages over the prior art are herewith provided in the followingdisclosure.

Set forth herein are several of the inventive features of the disclosedsystem and method for the transfer of cryogenic fluid. An automatedsystem for refueling and venting liquid hydrogen systems. A flangemating system including embedded electro-magnets, vacuum, and a roboticarm to provide compressive forces for sealing the mating flanges thuseliminating the need for bolts or clamps as required in prior art formanual mating of flanges. A flexible bellows to provide a collapsiblechamber to allow the internal nozzle to be inserted into the seal whilemaintaining the vacuum and nitrogen purge capability. A method of usinga flexible bellows vacuum and purge chamber that eliminates the need forexpensive and non-renewable helium gas for pre and post fluid transferpurging operations. A removable hinged cap that provides pressure reliefduring normal flight operations. A mechanism including a rotating shaftand gear drive that penetrates the vacuum chamber wall using a fluidicseal and mechanically drives the cap open during the refueling process,which enables automated robotic removal of the cap under vacuum andpurged conditions. A transfer tube nozzle compression fitting with aspecially designed tapered compression feature for compressing on atapered tank flange seal. A method for operating the apparatus thatallows for the safe, efficient, and rapid transfer of cryogenic fluidsunder automatic control using feed-back from a variety of sensors on thecondition and position of the apparatus and hydrogen tank.

Accordingly, one aspect of this disclosure relates to a refueling systemfor aircraft includes

a fuel storage container mounted on a support platform,

the support platform positionable above a refueling station providingspace for an aircraft beneath the support platform to permit positioningof an aircraft beneath the support platform for refueling, and

a connection system connectable to an aircraft to supply fuel from thestorage container to an aircraft located in the space.

Optionally, the fuel storage container includes a cryogenic fuel storagecontainer, and the connection system includes a refueling couplingassembly.

Optionally, the system further includes a sensor system configured toalign an aircraft with the connection system for supplying fuel to theaircraft.

Optionally, the system further includes a cryogenic fuel generator onthe support platform and a power source and control panel configured tocontrol operation of the cryogenic fuel generator to generate cryogenicfuel and the connection system for connection to an aircraft fuelsystem.

Optionally, the system further includes an isolating system configuredto protect the environment in which at least part of the connectionsystem is located during the coupling of cryogenic fuel from the fuelstorage container to an aircraft.

Optionally, the support platform is movable on wheels.

Optionally, the support platform is a movable trailer.

Optionally, the coupling system includes a cryogenic fuel transfersystem with insulation to minimize thermal conduction, a nozzle, anisolation space, and a seal to connect with a cryogenic fuel tank inletof an aircraft.

Optionally, the system further includes

positioned on the support platform an electrolyzer configured to convertwater to its constituent components hydrogen and oxygen, and

a refrigeration apparatus to refrigerate the hydrogen to cryogenicliquid hydrogen.

Optionally, the system further includes an alignment system includingsensors to facilitate aligning the fuel input of an aircraft with thecoupling system for transferring cryogenic fuel to the aircraft.

Another aspect relates to a cryogenic fuel transfer system, including,

a fuel nozzle configured to couple cryogenic fuel from a source to afuel tank inlet, and

a bellows positionable with respect to the nozzle and fuel tank inletwith respect to which the bellows may be moved for supplying fuel to thefuel tank inlet to provide a confined volume at which connection may bemade between the nozzle and the fuel tank inlet.

Optionally, the system includes a seal configured to seal with the fueltank inlet, and further includes a fluid connection to the confinedspace to evacuate gas from the confined volume.

Optionally, the system includes a vacuum source coupled to the fluidconnection to evacuate gas from the confined volume.

Optionally, the seal is configured to cooperate with vacuum in theconfined volume to enhance the sealing with the fuel tank inlet.

Optionally, the bellows is attached to move together with the nozzletoward and away from a fuel tank inlet respectively compressing andexpanding the bellows.

Optionally, the system further includes a mechanical support configuredto move the nozzle and bellows with respect to a fuel tank inlet.

Optionally, the system includes a controller configured to automaticallysense relative positions of the nozzle and bellows and of the fuel tankinlet to sense and to control alignment of the nozzle and bellows withrespect to the fuel tank inlet.

Optionally, the system includes a fuel tank inlet seal component and anozzle seal component, and wherein the seal components are cooperativeto seal connection between the nozzle and the fuel tank inlet to tend toavoid leakage of fuel.

Optionally, the system includes magnets cooperative to hold together theseal components to maintain the sealing.

Optionally, the magnets include electromagnets operable to pull togetherthe seal components to effect sealing and to release the pullingtogether of the seal components.

Optionally, the bellows is attached to the nozzle seal component.

Optionally, the system includes a movable cap positionable in theconfined volume movable selectively to open and to close access to thefuel tank inlet.

Optionally, the movable cap is attached to the fuel tank inlet.

According to another aspect, a seal for cryogenic fluid transferapparatus, includes

first and second flanges each having a substantially fluid impermeableportion and an opening through the fluid impermeable portion,

the flanges positionable with respect to each other to align theopenings with respect to each other to pass fluid therebetween,

a seal ring positionable between the fluid impermeable portions, and atleast one flange including serrations configured to bite into the sealring.

Optionally, both flanges have serrations.

Optionally, the seal ring further includes magnets configured to holdthe flanges together with the seal ring therebetween.

According to another aspect, a cryogenic fluid system, includes

a cryogenic fluid storage tank having an inlet,

a cap movable between open and closed positions with respect to theinlet,

a cryogenic fluid supply assembly including a nozzle positionable withrespect to the cryogenic fluid storage tank inlet to supply cryogenicfluid to the storage tank via the inlet,

an isolation assembly movable with respect to at least one of thecryogenic fluid storage tank inlet and the cryogenic fluid supplyassembly configured to provide a variable volume enclosure in which theinlet and nozzle may be coupled to transfer cryogenic fluid from thenozzle into the tank via the inlet.

Optionally, the isolation assembly includes a bellows.

Optionally, the cap is movable in the variable volume enclosure.

Optionally, the system further includes a vacuum source coupled toevacuate the space of gas.

Optionally, the system further includes a sensor configured to sensemovement and/or position of the isolation assembly.

Optionally, the system further includes a control responsive to thesensor to control movement of the isolation assembly.

Optionally, the system further includes a sensor configured to sense agaseous species in the volume.

Optionally, the system further includes a temperature sensor positionedto sense temperature of at least one of the variable volume or physicalparts of the system.

According to another aspect, a method for refueling a vehicle withcryogenic fluid, includes

effecting alignment of a refueling station and a vehicle,

sensing acceptable alignment,

moving a nozzle to position with respect to a fuel inlet of the vehicleand moving an isolation assembly to provided isolated space in which theconnection between the nozzle and fuel inlet is located,

sealing connection between the nozzle and fuel inlet, and

dispensing cryogenic fluid fuel from the nozzle to the fuel inlet.

Optionally, the effecting alignment includes using sensors to senseposition, and autonomously aligning the refueling station and vehicle.

Optionally, the method further includes opening a cap from closedposition closing the fuel inlet to an open position for insertion of thenozzle with respect to the fuel inlet.

Optionally, the sealing includes magnetically holding parts of a sealtogether.

Optionally, the method further includes vacuum purging the area of thenozzle and fuel inlet outside of the flow path of fluid from the nozzleinto the fuel inlet.

Optionally, the method further includes applying a vacuum in theisolated space to enhance sealing of the connection between the nozzleand fuel inlet.

Optionally, the method further includes performing a nitrogen purge ofthe isolated space after completing refueling of the vehicle.

According to another aspect, a system for cryogenic fluid transfer,includes

a cryogenic fuel tank including:

-   -   a tank body having at least one tank body opening between an        interior tank surface and an exterior tank surface;    -   a flexible gasket affixed to the tank body and surrounding the        at least one tank body opening while outwardly extending from        the exterior tank surface;    -   a cap mounted to the exterior tank surface and configured to        moveably cover and uncover the at least one tank body opening by        engaging and disengaging the flexible gasket;

a first embedded magnetic mating flange surrounding the flexible gasketand the cap; and

a cryogenic refueling assembly including:

-   -   a supply hose;    -   a robotic arm rigidly attached proximate to an opening in the        supply hose; and    -   a bellowed coupling assembly that bounds, at least in part, an        interior bellow volume that is defined between a compressible        wall surface and a proximal end wall, wherein the bellowed        coupling assembly is rigidly connected to the robotic arm and in        fluid communication with the opening in the supply hose, wherein        a distal end of the compressible wall surface is surrounded by a        second embedded magnetic mating flange, the bellowed coupling        assembly further includes:        -   a nozzle having a proximal end and a distal end, wherein the            nozzle proximal end is rigidly connected to the bellowed            coupling assembly proximal end and is in fluid communication            with the opening in the supply hose, wherein the nozzle            distal end is concavely configured to mate with the flexible            gasket;        -   a vacuum purge port disposed interior to the interior bellow            volume;        -   a heating element; and        -   at least one sensor configured to monitor at least one            condition of the interior bellow volume; and    -   a controller configured to monitor the at least one sensor and        drive the robotic arm in response to at least one condition of        the interior bellow volume.

According to another aspect, a method for cryogenic fluid transfer,includes the steps of:

-   -   initiating a refueling sequence when a cryogenic fuel tank        approaches a bellowed coupling assembly of a cryogenic refueling        assembly;    -   mating of a first embedded magnetic mating flange of the        cryogenic fuel tank and a second embedded magnetic mating flange        of the bellowed coupling assembly;    -   monitoring at least one condition of an interior bellow volume        of the bellowed coupling assembly through at least one sensor        mounted therein;    -   conditioning the interior bellow volume through vacuuming,        heating, and purging;    -   disengaging a cap from a flexible gasket affixed to the        cryogenic fuel tank, thereby uncovering an opening into the        cryogenic fuel tank;    -   moving a robotic arm to align a distal end of a nozzle of the        bellowed coupling assembly with the opening into the cryogenic        fuel tank;    -   moving the robotic arm towards the cryogenic fuel tank to        compress a compressible wall surface of the bellowed coupling        assembly;    -   engaging the distal end of the nozzle with the flexible gasket;    -   dispensing cryogenic fuel into the cryogenic fuel tank;    -   ceasing the dispensing of the cryogenic fuel into the cryogenic        fuel tank;    -   moving the robotic arm away from the cryogenic fuel tank to        uncompress the compressible wall surface;    -   disengaging the distal end of the nozzle from the flexible        gasket;    -   engaging the cap with the flexible gasket, thereby covering the        opening into the cryogenic fuel tank;    -   monitoring at least one condition of the interior bellow volume;    -   conditioning the interior bellow volume through vacuuming,        heating, and purging; and    -   unmating of the first embedded magnetic mating flange and the        second embedded magnetic mating flange.

Other objects and advantages of the disclosed system and method fortransfer of cryogenic fluids will be apparent from the followingdescription, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The concurrently filed figures represent various perspectives (e.g.,from above, below, side views, individual component views, combinedsystem views) of one embodiment of the present invention. A person ofordinary skill in the art would understand that the specific componentsdepicted in these figures are only representative and are not limiting.As such, the present invention does not lie in any single component, butrather in the collection of components described in their arrangement.And a person of ordinary skill would understand the present disclosureto teach the invention described as well as those embodiments thatreplace certain disclosed components for components that serve similarpurposes and will not disturb the novel features of the presentinvention.

FIGS. 1A and 1B, respectively, are a flow diagram showing two differentfluid transfer processes (a) pressurization and (b) pump.

FIG. 2 is an illustration of a UAV being refueled with liquid hydrogen.

FIG. 3 shows a flatbed trailer mobile liquid hydrogen refueling station.

FIGS. 4A, 4B, 4C, and 4D (sometimes referred to collectively as FIG. 4)are cross sections of the nozzle couple assembly in four differentpositions corresponding to disengagement, engagement, cap opening, andnozzle insertion.

FIG. 5 is a cross section of the fluid transfer refueling couplingassembly attached to the UAV liquid hydrogen tank.

FIG. 6 is a cross section of knife edge serrated flanges with gasketin-between.

FIG. 7 is a cross section of the refueling coupling assembly that showsthe mechanical gear mechanism for opening the spring loaded cap.

FIG. 8 is a cross section of the refueling coupling assembly connectedto a remote controlled robotic arm that uses various sensory input forcontrol.

FIG. 9 is a flow diagram of the method for refueling a UAV with liquidhydrogen using the refueling coupling assembly.

FIG. 10 is a diagram illustrating the use of a v-grove to center andguide the coupling assembly onto the tank flange.

FIGS. 11A, 11B, 11C, and 11D (sometimes referred to collectively as FIG.11) illustrate the four basic nozzle assembly positions that includedisengage, engage, cap opening, and nozzle insertion using two nozzleassemblies; one for liquid fill and one for gas vent.

FIGS. 12A, 12B, 12C, and 12D (sometimes referred to collectively as FIG.12) illustrate the four basic nozzle assembly positions that includedisengage, engage, cap opening, and nozzle insertion using a singlenozzle assembly with both a liquid fill and a gas vent within theassembly.

FIGS. 13A, 13B, 13C, and 13D (sometimes referred to collectively as FIG.13) illustrate the four basic nozzle assembly positions that includedisengage, engage, cap opening, and nozzle insertion using a singlenozzle assembly with a concentric tube liquid fill and a gas vent withinthe assembly.

FIG. 14 is a flow diagram describing a method for the transfer ofcryogenic fluids into and out of a cryogenic tank.

DESCRIPTION

The disclosed cryogenic refueling system and method can be used for thetransfer of liquid hydrogen and venting of gaseous hydrogen in eitherstationary ground applications or inflight applications as will bediscussed further.

FIG. 1 is discussed above.

As shown in FIGS. 2-5 an embodiment of the disclosed system and methodfor the transfer of cryogenic fluids begins with the process ofrefueling a UAV 50 with liquid hydrogen. The liquid hydrogen tank 38 ordewar on board the UAV 50 is designed to contain 21 to 33 Kelvin liquidhydrogen at tank pressures ranging from 15 psia to 200 psia. The UAV 50can be any type of aerial vehicle such as fixed-wing or rotary type. Thesystem and method for the transfer of cryogenic fluid disclosed hereinalso or alternatively may be used to transfer cryogenic fluids to othervehicles, e.g., cars, trucks, ships, other aircraft, and so on. Afixed-wing aircraft is depicted in the figure. The UAV is flyingautonomously when the aircraft liquid hydrogen quantity sensor indicatesthe UAV needs to refuel. The autopilot then flies the UAV to the nearestairport with liquid hydrogen refueling. The UAV autonomously lands andtaxies over to the refueling station using the Global Positioning System(GPS) coordinates. As the UAV approaches the station, additional sensorsare used such as optical or laser detection to position the UAV underthe refueling coupling assembly. An optical system 60 inspects thehydrogen tank flange 13 (seal portion or seal component) for finalalignment and detection of any potential problems that would put theprocess on hold. Once permissions are given by the system, the processas described below is implemented. Once the process is complete and therefueling coupling assembly 20 is removed, the UAV 50 taxies back to therunway and continues flight operations.

FIG. 3 shows a flatbed trailer 39 that serves as a mobile liquidhydrogen refueling station that can be parked at any airport or fieldoperation for UAVs. The refueling station 39 has on it a number ofcomponents for the generation and storage of liquid hydrogen from water.At one end of the flatbed support platform is a cabinet 40 for the hookup of local utilizes such as power, water, and gaseous nitrogen forpurging. The cabinet contains storage tanks of water and bottles ofgaseous nitrogen that are replenished from the local supply hook ups.The power and water flow into the electrolyzer 41 to generate oxygen andhydrogen gas as shown by the arrow 57. The electrolyzer 41 can be aProton Exchange Membrane type. The oxygen can be vented to atmosphere orused in other processes that are not discussed here. The gaseoushydrogen flows to the liquefier 42 where the hydrogen is chilled downand liquefied. The electrolyzer 41 and liquefier 42 are a cryogenic fuelgenerator. Arrow 58 shows the flow of gaseous hydrogen from theelectrolyzer 41 to the liquefier 42. The liquefier needs to be sizedwith a cryogenic refrigerator or cryocooler with sufficientrefrigeration power to make liquid hydrogen. A catalyst may be insertedin the dewar or flow lines to rapidly conduct the ortho-hydrogen topara-hydrogen conversion prior to flowing the liquid hydrogen into thestorage dewar 46 as shown by arrow 59. The UAV 50 is shown under thecutout 51 in the middle of the flatbed trailer 39. The cutout 51 is anopening in the flatbed that allows direct and indirect connection ofsignals and of fluids between the UAV 50 and the refueling system. Therefueling coupling assembly 20 is shown disengaged from the UAV 50. Whenengaged, liquid hydrogen is pressure fed from the storage dewar 46 usingthe vaporizer 47 to use some of the liquid to pressurize the dewar. Asthe UAV liquid hydrogen tank 38 is refilled, any vapor that is generatedgoes out the hard plumbed vent 43. A structure 44 used over the cutout51 supports all plumbing, hoses, vents, hard plumb connections, tubing,instrument wires, lighting, sensors such as hydrogen detectors, opticalsensors 60 for monitoring position and operations, and any valvingassociated with the refueling station. A fuel cell 48 that consumesresidual hydrogen gas from the vent or the dewar is used to providepower to operate the system when utility hook up is not available due toplanned or emergency operations. A control panel 49 is located at an endof the flatbed trailer 39 to house all the controls, power supplies,electrical contacts, safety systems, and local readouts to operate therefueling station on an as needed bases. Once filled, the UAV 50proceeds through the other side of the flatbed trailer 39 and heads outto the runway. The refueling station 39 s including the flatbed trailer39, can then be transported to any airport to support the liquidhydrogen UAVs.

The method of refueling is as follows and is illustrated in FIG. 4 withthe main components shown in FIG. 5. FIG. 4 shows the four main types ofpositions the refueling coupling assembly 20 goes through during nominaloperations. The first position (A) is the disengaged position where therefueling coupling assembly 20 is hovering above the hydrogen tankflange 13. The next position (B) is the mating of the flanges with thebellows 1 still in the extended position. The next position (C) showsopening of the cap 16 exposing the tank flange seal 15. The finalposition shown (D) is the engagement of the nozzle 3 on the tank flangeseal 15. The bellows 1 is expandable and contractible. In its contractedstate for fueling, the volume or space 22 within the bellows provides anisolation space or volume to avoid leakage of gas (or other species) tothe environment external of the bellows. Also, a vacuum (discussedbelow) may be applied to the isolation space or volume to remove anyspecies therefrom, e.g., during the process of transferring cryogenicfluid.

FIG. 5 shows the refueling coupling assembly 20 brought into contactwith the tank flange assembly 21, which is constructed within the fueltank 38. The mating surfaces are the coupling flange 11 and the tankflange 13, which are cryogenic fluid fuel impermeable. An opening ineach flange aligns with each other for the nozzle to pass fuel into thefuel tank inlet. The magnets 10, 12 buried within the flanges 11, 13 areactivated to maintain the connection between the two assemblies. One orthe other or both flanges have serrations 55 (FIG. 6).

The serrations 55 shown in FIG. 6 are knife edges that bite into thecoupling flange gasket 54 material and make a seal on the tank flange13. The coupling flange gasket 54 is flat with the preferred materialbeing Kel-F or material having similar or suitable properties. A vacuumis pulled using a vacuum pump through the vacuum/purge port 2. Thevacuum/purge port 2 is a tube in fluid contact with the vacuum space 22to which a vacuum hose is attached leading to a vacuum pump. Thevacuum/purge port 2 is also connected into a purge gas source via a teein the line and tubing leading to a source of high-pressure purge gassuch as nitrogen. A heating element 53 is located inside the couplingassembly to warm components when necessary to reach certain temperaturecriteria during the refueling process.

FIG. 7 is a cross section of the refueling coupling assembly 20 thatshows the mechanical gear mechanism for opening the spring loaded cap16. As is shown in FIG. 7, the spring loaded cap is in its fully openedposition 17 while the bellows is in its fully contracted position 18. Arotary gear drive shaft 36 is linearly actuated into the vacuum space 22and engages the spring hinge 7, which has a mating gear. The rotary geardrive shaft 36 may also provide a path for electrically grounding theliquid hydrogen tank 38. The spring hinge 7 provides a normally closedcap 16 and requires a force to reverse the spring and open the cap. Thespring hinge 7 is supported off the tank flange face 14 by the hingebase 8. The rotary gear shaft 36 penetrates the coupling wall 9 from theside using a ferro-fluidic rotary seal 37. The coupling wall 9 connectsthe other end of the bellows to the coupling flange 11. The couplingwall 9 provides a solid surface to mount feed-through penetrations topass devices such as wires and mechanical components into the vacuumspace 22 from the outside, including the ferro-fluidic rotary seal 37.The ferro-fluidic rotary seal 37 is designed to provide mechanical(translational and rotational) access to vacuum spaces without breakingthe vacuum seal. The rotary gear is activated in a rotational mode usingan intrinsically safe electric drive motor 52 and provides the forceneed to reverse the spring of the spring hinge 7 and raise the cap arm6, which the cap 16 is mounted to. The cap 16, which is the primaryliquid hydrogen tank sealing device, is designed with identical sealingfeatures as the tube nozzle compression fitting 5.

The spring hinge 7 is designed to allow pressure relief of the liquidhydrogen tank 38. When the UAV 50 consumes less hydrogen fuel than thenatural heat leak of the liquid hydrogen tank 38, which generatesboil-off gas, the tank will pressurize. The tank is designed to operateat a maximum expected operating working pressure and a relief device isnecessary to keep the tank from bursting. The spring hinged cap 16 isthe relief device. Other methods of holding the cap in place with aforce can be envisioned include other combination of spring loadedclamps, belleville washers, magnets, and cryogenic “rubber” bands madeout of Kapton, which is flexible at cryogenic temperatures. The springhinge 7 also has the feature to re-seat on the tank flange seal 15 oncethe pressure has been relieved because of the restoring force of thespring of the spring hinge.

An alternative embodiment of the cap 16 is one that has a flapper insidethe cap 16 that would open when pushed down by the refueling tube nozzle3. In this configuration the spring hinge cap 16 would still serve as apressure relieve device but would not have to be removed for refueling.The flapper would have to be spring loaded in order to be normallyclosed. A cryogenic seal would need to be included in the passagewaythrough the cap 16 or as part of the nozzle 3. This can be accomplishedwith Kel-F o-rings on the outer diameter of the nozzle 3 or the innerdiameter of the cap 16.

The robotic arm 24 (FIGS. 3 and 8) then drives the bellows flange 4down, compressing the bellows 1 until the fluid transfer tube nozzlecompression fitting 5 (FIG. 5) engages the tank flange seal 15. Thebellows flange 4 forms one end of the vacuum space 22 by attaching thebellows to it via welded construction. The robotic arm 24 as shown inFIG. 8 is connect to the nozzle vacuum jacket 33, which is connected tothe bellows flange 4. The robotic arm when stationary and in the properposition keeps the bellows 1 from collapsing while the vacuum space 22is evacuated to at least 10⁻⁴ torr. The nozzle 3 is shown in FIG. 8 inits engaged state for refueling 19 by sealing on the hydrogen tank sealand the bellows is in fully compressed state 18.

The tube nozzle 3 is designed to allow liquid hydrogen to flow from thevacuum jacketed hose 23 into the UAV liquid hydrogen fuel tank. The tubenozzle 3 is machined fabricated with an integral compression fitting 5designed to compress on the tank flange seal 15. The tank flange sealshould have a taper angle of between about 25 and about 45 degrees,preferably about 35 degrees. The tank flange seal 15 is held in place bydirect bolting to the tank flange face 14 or by the over-lay of a tankflange seal ring 56 (FIG. 5), which can then compress the tank flangeseal 15 to the tank flange face 14. The transfer tube nozzle 3 does notneed to be centered within the bellows 1 due to the controllability ofthe robotic arm 24 to place mating flanges 11, 13 in their properposition. The transfer tube nozzle 3 is insulated with insulation 34 tominimize heat leak. The preferred insulation is multilayer insulation(MLI) with alternating layers of double aluminized Mylar and Dacronnetting spacers. Alternative insulation than be used in combination withMLI is spray-on foam insulation (SOFI). Insulation 35 (FIG. 5) such asSOFI is also placed over the tank flange face 14 and tank flange seal 15to minimize heat leak into the tank. The vacuum space 22 is continued tobe pumped on. The liquid hydrogen is then transferred into the fueltank.

When the filling process is complete the bellows 1 are raised up and thecap arm 6 is placed back down onto the tank flange seal 15. The vacuumsystem is maintained for a period of time to remove residual hydrogengas and then nitrogen is purged into the bellows area. Temperaturesensors 31 on the cap 16 are monitored for nitrogen freezingtemperatures. Other temperature sensors can be installed to monitor walltemperatures to minimize freezing of water vapor. A heating element 53within the assembly can be used to increase the warm up time asrequired.

In FIG. 8 the measurement and control aspects of the innovation areshown. The figure shows the nozzle vacuum jacket 33 that is welded tothe bellows flange 4. A vacuum jacketed transfer hose 23 is welded tothe outside nozzle vacuum jacket 33 and the inside nozzle 3. The vacuumjackets are necessary to minimize heat leak to the liquid hydrogen thatwill cause vaporization. The robotic arm 24 attaches to the nozzlevacuum jacket 33. The robotic arm may be a movable mechanical supportfor one or more parts to which it is attached. The robotic arm iscontrolled by any number of intrinsically safe electric motors 25 toprovide the degree of freedom needed to accomplish the assembly matingprocess. The motors are intrinsically safe for operation in a hydrogenenvironment or may be purged with nitrogen gas. The controller 26controls the robotic arm 24 by remote operation or by automaticoperation using feed-back from a number of sensors including force 27,pressure 28, displacement 29, species 30, temperature 31, and position32 sensors.

Examples of feed-back information for control include the following. Theforce sensor 27 measures the amount of force being exerted onto thenozzle 3 by the robotic arm 24, which is used by the controller 26 tokeep the forces within predetermined limits for maximized sealingcapability not to exceed structural limits on the equipment or the UAV50. The species sensor 30 measures the amount of hydrogen and oxygen inthe vacuum volume 22, which is used by the controller 26 to compare withflammability limits thus enabling the a safe filing process to proceedor continue. Exceeding flammability limits would result in an emergencyshutdown where the filling process would discontinue. Pressuremeasurements 28 within the assembly are used to determine vacuum levels,over pressurization levels, or nominal pressure levels that depending onwhich steps in the process, provide information for safety purposes andequipment operational condition monitoring. The temperature sensors 31provide information on the status of the equipment in order to proceedto the next step. The temperature of the cap 16 after the fillingprocess is complete is of interest to maintain above 90 K so that liquidoxygen will not form on the cap after the assembly is disengaged fromthe system and exposed to ambient air conditions. The displacementsensor 29 on the bellows 1 determines the position of the nozzle 3 andenables the controller 26 to know the bellows 1 is operating withinacceptable limits.

FIG. 9 shows the apparatus attached to the UAV liquid hydrogen tank forboth the liquid fill and the vent. The figure by virtue of the arrowsshows the liquid hydrogen being pressure transferred out of the storagedewar through hard plumbing to the flexible vacuum jacketed hose 23.Also shown is a hard plumbed vent attached to a second apparatus that isused for venting the tank during the filling process.

To protect the magnets in the tank flange 13 from picking up debris whennot being refueled, a removable cover could be attached. The preferredmaterial is Teflon that can withstand the cold temperatures on the tank.An alternative material could be Kel-F.

An alternative to the permanent magnets 10 are electro-magnets that canbe actively controlled.

An alternative design to the coupling flange 11 and to the tank flange13 is to provide a self-centering bevel in v-shaped groove. (See FIG.10). Alternatives to permanent magnets as originally depicted include:Ring-shaped Halbach array of permanent magnets; permanent magnets inyoke; electromagnets in yoke (powered to engage), permanent magnets inyoke with opposing electromagnet (powered to release). Permutationsinclude: magnets on the refueling assembly and iron (or nickel or otherferromagnetic material) on the tank (Nickel's crystal structure is FCC(face centered cubic) so it should not have a ductile-brittletransition); magnets on tank and iron on refueling assembly; or magnetson both.

An alternative design to the liquid hydrogen transfer tube nozzle 3 isto add a bevel to the end for easy insertion into the seal 15.

The bellows 1 used in the described invention maintains a vacuum jacketaround the tube nozzle 3 when the refueling coupling assembly 20 issealed against the tank flange 13. This application of a bellows differsthan other uses of the bellows in that it is not permanently attached toboth ends of the piping system. In addition, the bellows 1 is activelycompressed and expanded when the robotic arm 24 is actuated to insertthe tube nozzle 3.

FIG. 11 illustrates a sequence of events for the refueling of a UAVliquid hydrogen tank 38 using the innovative refueling coupling assembly20. Once the UAV 50 is positioned directly under the refueling couplingassembly 20 the nozzles are disengaged as shown in FIG. 11A. In FIG. 11Bthe nozzle assembly 20 is brought in contact with the tank flange 13using the robotic arm 24. Magnetic coupling of the two flanges 11, 13 isconducted using the electro magnets 12 buried inside the flanges 11, 13.The attractive force of the magnets puts pressure on the sealing surfacegasket 54 between the two flanges 11, 13 to create a vacuum tight seal.The bellows 1 at this step are fully expanded. In FIG. 11C the cap 16 isopened, e.g., via a drive gear 36. The bellows 1 is still fullyexpanded. The final step shown FIG. 11D is the movement of the nozzleinto the LH2 (liquid hydrogen) tank receptacle to seal on the tankflange seal 15. The tube nozzle 3 is forced down onto the sealingsurface using the robotic arm 24. In FIG. 11 there are two separatenozzle coupling assemblies 20, one for the liquid fill and one for thevent. Each fluid is transferred through their respective flexible hoses,which attach to the refueling coupling assembly 20 and the flexible hoseat one end.

FIG. 12 shows the same sequence as in FIG. 11 only that in thisconfiguration only one vacuum space 22 is formed with the bellows 1.Inside the vacuum space 22 are two nozzles one for liquid and one forgaseous venting. There are two caps 16 that are both opened at the sametime. There are two gear drives.

FIG. 13 shows the same sequence as in FIG. 11 only that in thisconfiguration only one vacuum space 22 is formed with the bellows 1 andthe nozzle includes a concentric tube configuration. One of the tubes isfor the vent and one is for the liquid fill. Each flow path is separatebut only one liquid hydrogen tank penetration is required along withonly one cap 16.

A method for transfer of liquid hydrogen using the described inventionis presented in a flow diagram 100 in FIG. 14 and is described herein.The steps of flow diagram 100 are labeled as discussed below. The methodapplies to both on the ground refueling operations as well as in-flightrefueling. For on the ground refueling, the UAV 50 will land near therefueling station and the autopilot will taxi the UAV 50 over to therefueling station where it will park underneath the refueling station.Position sensors 32 provide information on the relative location of therobotic arm 24 and the coupling flange 11 with respect to the UAV 50fuel tank flange 13. The position sensor 32 will align the refuelingcoupling assembly 20 with the fuel tank flange 13. The magnets 10 in theflanges 11,13 will activate and attract the flanges to each othercreating a seal. Optical sensors 60 within the assembly visually inspectthe liquid hydrogen refueling tank flange 13 and cap 16. Once thedecision has been made to refuel, e.g., by an appropriately programmedcontroller or processor, or is otherwise made, e.g., based on video datacomparisons with a baseline configuration, the vacuum pump is activatedand pumps down the vacuum space 22 to create a vacuum. Heating element53 is activated to drive off moisture and other gases out of thechamber. The mechanical cap drive shaft 36 is translated into the vacuumspace 22 where the gear on the drive and the gear on the spring hinge 7are engaged. The mechanical drive is then rotated by an intrinsicallysafe motor 52 until a position sensor 32 indicates the cap is fullyremoved from the opening, exposing the tank flange seal 15. The heatingelement 53 is deactivated. The robotic arm 24 pushes the nozzlecompression fitting 5 down into the tank flange seal 15. The vacuumpurge is activated again and the pressure 28 is measured until itreaches the desired level. The liquid hydrogen fill valve, which is partof the storage dewar 46 is opened and liquid is pressure transferredinto the UAV 50 fuel tank 38 until a sensor on-board the UAV 50indicates full or alternatively a liquid/vapor sensor 70 inside thetransfer tube nozzle 3 indicates full or another fill level. The tubenozzle 3 is then removed automatically by the robotic arm 24 until thebellows 1 displacement measurement 29 indicates it is back in itsoriginal position. The cap 16 is replaced by reversing the drive gearshaft 36. The drive gear shaft 36 is moved back into its startingposition. The heating element 53 is turned on to warm up the internalsof the vacuum space 22. A nitrogen purge is initiated once thetemperature sensors 31 are above 90 Kelvin. Once temperatures are nearambient the magnets 10 in the flanges are released and the robotic arm24 removes the refueling coupling assembly 20.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theinvention. Aspects of the invention described in the context ofparticular embodiments may be combined or eliminated in otherembodiments. Further, while advantages associated with certainembodiments of the invention have been described in the context of thoseembodiments, other embodiments may also exhibit such advantages, and notall embodiments need necessarily exhibit such advantages to fall withinthe scope of the invention. Accordingly, the invention is not limitedexcept as by the appended claims.

We claim:
 1. A cryogenic fluid system, for a cryogenic fluid storagetank having an inlet and, a cap movable between open and closedpositions with respect to the inlet, the cryogenic fluid systemcomprising: a cryogenic fluid supply assembly including a nozzleconfigured to move vertically with respect to the cryogenic fluidstorage tank inlet to supply cryogenic fluid to the storage tank via theinlet, an isolation assembly movable with respect to at least one of thecryogenic fluid storage tank inlet and the cryogenic fluid supplyassembly configured to provide a confined volume in which the inlet andnozzle may be coupled to transfer cryogenic fluid from the nozzle intothe tank via the inlet; a cryogenic fuel storage container mounted on asupport platform, and the support platform positionable above arefueling station providing space for an aircraft beneath the supportplatform to permit positioning of the aircraft beneath the supportplatform for refueling with cryogenic fuel.
 2. The cryogenic fluidsystem of claim 1, the isolation assembly comprising: a bellowspositionable with respect to the nozzle and the inlet with respect towhich the bellows move to provide the confined volume inside of whichconnection between the nozzle and the inlet occurs.
 3. The cryogenicfluid system of claim 2, comprising: at least one magnet assemblydisposed at a bottom end of the bellows for magnetically engaging one ormore magnetic elements adjoining the inlet to produce the confinedvolume.
 4. The cryogenic fluid system of claim 3, wherein the at leastone magnet assembly cooperates with the one or more magnetic elementsadjoining the inlet to put pressure on a sealing gasket to provide theconfined volume with a vacuum tight seal.
 5. The cryogenic fluid systemof claim 2, comprising a controller configured to automatically senserelative positions of the nozzle and bellows and of the inlet to senseand to control alignment of the nozzle and bellows with respect to theinlet.
 6. The cryogenic fluid system of claim 1, the isolation assemblycomprising a seal configured to seal with the inlet, and furthercomprising a fluid connection to the confined volume to evacuate gasfrom the confined volume.
 7. The cryogenic fluid system of claim 6, theisolation assembly comprising a vacuum source coupled to the fluidconnection to evacuate gas from the confined volume.
 8. The cryogenicfluid system of claim 2, wherein the cryogenic fluid storage tankcorresponds to an aircraft and the nozzle engages the inlet of theaircraft vertically to supply cryogenic fuel from the storage containerto the storage tank of the aircraft.
 9. The cryogenic fluid system ofclaim 2, wherein the support platform is movable on wheels.